Figures published today that show the rise in the number of people killed and seriously injured on the UK's roads last year are truly shocking only when you know just how successful we had been in the past decade at reducing the volume of pain and misery experienced by thousands of people every year.

A 2% rise in the dead and injured may not sound significant to those not personally affected by a crash or collision, but it is the first rise for 16 years. During the heyday of the so-called war on motorists, the casualty rate came tumbling down but, since budgetary cuts have begun to take their toll on road policing, safety budgets and speed cameras, the figures have started to turn upwards. In short, we are in danger of returning to the old culture in which the car is king – putting those most vulnerable on our roads, namely cyclists and pedestrians, at greater risk again.

London had the fastest casualty decline of any region. In 2010 there were 685 fewer children killed or seriously injured on London's roads than in the late 1990s. As the previous mayor's road safety ambassador, I'm sure that, if we hadn't spent the money we did and made the changes we did, many of those 685 would not be walking, running and skipping around today.

There was a 10-year plan and it worked. When London hit the national targets for casualty reduction five years early, we set harder targets and spent even more money on 20mph zones and traffic police. We saved lives and relieved the NHS of a huge bill. Then Boris Johnson was elected mayor and the road safety budget was more than halved, the traffic police faced cuts and he introduced a policy of "smoothing traffic flow". This policy includes the rephasing of traffic lights to give less time to pedestrians, getting rid of signalled pedestrian crossings and telling his engineers not to introduce safety measures on roads where they might reduce traffic capacity. The result is that a nine-year decline in casualties went into reverse from 2008 onwards and, we now have 1,000 more people injured on London's roads every year.

A similar pattern is emerging with the national figures since the change of government. The whole package of ambitious targets with national and local strategies has been junked. While these latest figures are dismissed by transport secretary Justine Greening with talk of exceptional weather, no acknowledgement is made of the sudden growth in the number of pedestrians and cyclists killed or seriously injured. Johnson was equally dismissive when I first approached him about the rise in total casualties. For two years London was the only region in the country to be on an upward trend; now I think the rest of the country is on the same course.

The mayor will no doubt argue that he has bucked the national rise as the total number of killed and seriously injured on the roads has fallen in London. But the reality is that London accurately reflects the UK-wide trend towards cars becoming safer, rather than roads themselves. In London, there were 223 fewer car occupants killed or seriously injured, but 171 more pedestrians and cyclists. Johnson called this "good news" in today's press release; I call it an undeclared war on the most vulnerable people who use our roads.

The mayor again said on Wednesday night that London's roads were getting safer for cyclists. Despite a huge jump of almost a quarter in the number of cyclist casualties in one year, the complacency remains. Johnson is a mayor who cycles. The coalition government is also full of ministers who cycle. They clearly care, but this "car is king" culture permeates all their decisions on budgets and priorities. The question remains about how we are to change that. Reinvestment and a return to robust targets would be a starting point at least.